Known agents possessing an antiviral activity include those compounds which may inhibit viral DNA synthesis, such as ara-A and acyclovir, an those which may inhibit reverse transcriptases of retroviruses, such as suramin, ribavirin and AZT (azidothymidine).
Retroviruses are RNA viruses of which RNA is transcribed into DNA with reverse transcriptase. The etiologic agent causing acquired immunodeficiency syndrome (AIDS) is a retrovirus called HTLV-III (human T-cell lymphotrophic virus type III), LAV (lymphadenopathy-associated virus) or HIV (human immunodeficiency virus).
AIDS develops in the form of Kaposi's sarcoma and opportunistic infections such as Pneumocystis carinii pneumonia (PCP), candidiasis, aspergillosis and amebic colitis, which arise due to a depressed immune response of a living body. AZT is the only drug known as an agent capable of inhibiting the growth of HIV.
When infected with the AIDS-causing virus, the subject becomes an asymptomatic carrier (AC), then develops AIDS related complex (ARC) and eventually overt symptoms of AIDS.
Those antiviral agents which act as inhibitors of viral reverse transcriptases are fairly toxic to normal cells and have marked side effects on patients, thus leading to debility of body besides prolongation of life upon administration.
An object of this invention is to provide antiviral agents effective in suppressing cellular infection of AIDS-causing virus and/or inhibiting further progress of the infection into ARC and into AIDS, hence useful in the treatment of AIDS, by means of a low toxic substance which may inhibit reverse transcriptases and have other mechanisms of action.